JP5757585B2 - Injection molding machine - Google Patents

Description

The present invention relates to an injection molding machine in which a screw of an injection apparatus is operated by an electric motor and a mold clamping cylinder of a mold clamping apparatus is operated by hydraulic pressure.

An injection molding machine is required to have each element of precise operation, energy saving, compactness of the molding machine, and cost reduction. In particular, for an injection device that requires precise operation, it is desirable to operate the screw with a servo motor. As for the horizontal mold clamping apparatus, the one using the mold clamping cylinder can make the molding machine more compact than the one using the toggle mechanism. Furthermore, for the mold clamping device of a large injection molding machine, there is a problem that the electric motor necessary for driving is not in time for a general-purpose product and the cost becomes very expensive, or there is no electric motor that can be handled, In many cases, a clamping cylinder operated by hydraulic pressure is used.

In response to the above requirements, there is an injection molding machine in which the operation of the screw of the injection device is operated by an electric motor and the operation of the clamping cylinder of the mold clamping device is hydraulically operated. The thing of FIG. 8 of patent document 1 is known. In Patent Document 1, a screw of an injection device that requires precise operation is operated by a servo motor, and a mold clamping cylinder that is hydraulically operated is used as the mold clamping device. Further, as disclosed in Patent Document 2, an electric motor is used as the movable die plate moving means in the mold clamping device, and a hydraulic mold clamping cylinder is used as the mold clamping mechanism. In Patent Document 2, energy saving is achieved by controlling the rotation speed of the pump by an inverter or a servo motor. Further, Patent Document 3 describes that a pump that is operated by a plurality of servo motors is used in which the entire injection molding machine is operated by hydraulic pressure, and one pump is stopped as necessary.

JP 2012-20415 A (0042, FIG. 8) Japanese Patent Laying-Open No. 2003-181895 (Claim 1, FIG. 1) JP 2007-69501 A (Claim 1 FIG. 1)

Certainly, the operation of the screw of the injection device with the electric motor as in Patent Document 1 can perform the control at the time of injection with high accuracy, and at the same time, the energy saving of the injection device can be realized. Conventionally, however, the mold clamping device has been operated by a large pump that constantly rotates the pump, so that it has not been possible to achieve sufficient energy saving for the entire injection molding machine. Further, since Patent Document 2 uses an electric motor for the movable die plate moving means, it is possible to realize energy saving and high-speed and high-precision movement of the moving means. However, there is no indication of the drive system of the injection device, and the operation of the other parts of the mold clamping device is performed by a large pump that always rotates the pump. could not. Furthermore, since Patent Document 3 uses a plurality of pumps operated by a servo motor and stops one of the pumps as necessary, the hydraulic mechanism can save energy. However, since all the mechanisms of the injection molding machine are controlled by hydraulic pressure, energy saving is not sufficient compared to the one that directly operates the injection device by an electric motor such as a servo motor, and the injection device is controlled with high accuracy. There was a problem that I could not.

Therefore, the present invention relates to an injection molding machine that uses hydraulic pressure as a mold clamping mechanism of a mold clamping device, and uses an electric motor for the injection device to achieve high accuracy and energy saving while requiring mold clamping for a long time. An object of the present invention is to provide an injection molding machine that can also save energy for the fastening device.

An injection molding machine according to claim 1 of the present invention is an injection molding machine in which the operation of a screw of an injection device is performed by an electric motor and the operation of a clamping cylinder of the mold clamping device is hydraulically operated . Servo motor for metering, first pump in which electric motor of driving source is always rotated , and electric motor of driving source is stopped or rotated at minimum rotation speed when any actuator other than clamping cylinder is operated And a second pump, and the mold clamping cylinder is operated by combining the hydraulic oil from the first pump and the hydraulic oil from the second pump .

The injection molding machine according to a second aspect of the present invention is the injection molding machine according to the first aspect, wherein the operation of the mold opening / closing mechanism of the mold clamping device is performed by a servo motor of the mold opening / closing mechanism, so Is characterized in that the rotation of the second pump is stopped or rotated at the minimum rotational speed.

The injection molding machine according to a third aspect of the present invention is the injection molding machine according to the first or second aspect, wherein the rotation speed of the first pump is controlled by an inverter, and the second pump is controlled by a servo motor. The rotational speed is controlled.

According to a fourth aspect of the present invention, there is provided the injection molding machine according to any one of the first to third aspects, wherein the clamping cylinder is operated by a valve operated by a pilot pressure, and the pilot pressure is the first pressure. It is ensured by the operation of the pump.

Injection molding machine of the present invention, in an injection molding machine for performing the hydraulic actuation of the clamping cylinder performs mold clamping device the operation of the screw of the injection device by an electric motor, a servo motor for injection, and a servo motor for weighing A first pump in which the electric motor of the drive source is always rotated, and a second pump in which the electric motor of the drive source is stopped or rotated at the minimum rotation speed when any actuator other than the clamping cylinder is operated. Since the mold clamping cylinder is operated by joining the hydraulic oil from the first pump and the hydraulic oil from the second pump, it is possible to improve the accuracy and energy saving of the injection device and to save energy of the mold clamping device. Can be achieved.

It is explanatory drawing of the hydraulic circuit and control apparatus of the injection molding machine of this embodiment. It is a time chart figure which shows each process of the injection molding machine of this embodiment. It is a figure which shows the action | operation of the pump at the time of cut-off control of the injection molding machine of this embodiment. It is a figure which shows the action | operation control of pumps, such as a mold closing process of the injection molding machine of this embodiment. It is a figure which shows the action | operation control of the pump of the mold clamping process of the injection molding machine of this embodiment. It is a figure which shows the action | operation control of the pump of the powerful mold opening process of the injection molding machine of this embodiment. It is a figure which shows the operation control of the 2nd pump of the taking-out process of the injection molding machine of this embodiment.

An injection molding machine 11 according to an embodiment of the present invention will be described with reference to FIG. The injection molding machine 11 operates the screw 14 of the injection device 13 provided on the bed 12 by the electric motors 15 and 16, and operates the mold clamping cylinder 18 of the mold clamping device 17 also provided on the bed 12. This is an injection molding machine 11 performed by hydraulic pressure. First, the injection device 13 will be described. The screw 14 is provided in an inner hole of the heating cylinder 19 so as to be rotatable and to be able to move forward and backward. A nozzle 20 is provided in front of the heating cylinder 19. The front plate 21 to which the heating cylinder 19 is fixed is provided with a material supply hole 22 facing the inner hole of the heating cylinder 19. Further, a cylinder portion of a hydraulic cylinder 24 for nozzle touch of a nozzle touch mechanism in which the entire injection device 13 is moved forward and backward and the nozzle 20 is brought into contact with the fixed mold 23 is attached to the front portion of the front plate 21. . The actuator of the nozzle touch mechanism may be a mechanism using an electric motor and a ball screw.

Further, a back plate 25 is provided behind the front plate 21 (right side in FIG. 1), and a pusher plate 26 (intermediate plate) is provided between the front plate 21 and the back plate 25 in the bed 12. It is provided so that it can move forward and backward. The back plate 25 is fixed with an injection servo motor 15 (electric motor) for moving the screw 14 back and forth, and a drive shaft of the servo motor 15 and a ball screw are connected to each other. A ball screw nut is fixed to the pusher plate 26. The ball screw is inserted into the ball screw nut, and the pusher plate 26 is moved forward and backward by rotating the ball screw. Further, a metering servo motor 16 (electric motor) for rotating the screw 14 is fixed to the pusher plate 26, and the drive shaft of the servo motor 16 is connected to the rear of the screw 14 via a belt and is connected to the pusher plate 26. It is connected with a pulley fixed to a rotating shaft that is pivotally supported. The injection device 13 may be composed of two plates in which an injection servomotor (electric motor) is fixed to the front plate 21 and a measuring servomotor (electric motor) is fixed to the back plate. . The injection device 13 in which the actuator for driving the screw 14 as described above is an electric motor can be controlled with high accuracy at the time of injection or weighing, and is excellent in terms of energy saving.

Next, the mold clamping device 17 will be described. Mold clamping cylinders 18 are provided in the vicinity of the four corners of a fixed plate 27 that is fixed to the bed 12. The rod of the mold clamping cylinder 18 constitutes a tie bar 28, and the tie bar 28 is inserted into bushes (guide holes) near the four corners of the movable plate 29. A conical hole through which the nozzle 20 of the injection device 13 is inserted is formed in the center of the fixed platen 27. Further, rods of the hydraulic cylinder 24 for nozzle touch are attached to both sides of the hole of the fixed plate 27. Further, in the fixed plate 27, a fixed mold 23 is attached to the surface of the reflecting device, and the nozzle 20 is brought into contact with the fixed mold 23 through the hole. Servo motors 31 (electric motors), which are actuators of the mold opening / closing mechanism, are fixed to both side surfaces of the fixed platen 27, and a ball screw 32 is connected to the drive shaft of the servomotor 31. Ball screw nuts 33 are fixed to both side surfaces of the movable platen 29, and the ball screw 32 is inserted through the ball screw nut 33. With this mechanism, in this embodiment, the movable platen 29 is moved (opening / closing) by an electric motor. The servo motor 31 of the mold opening / closing mechanism may be fixed to the bed 12, and the mold opening / closing mechanism may be operated by a hydraulic cylinder.

A locking portion 34 having a plurality of grooves is provided on the outer periphery of the tie bar 28, and a half nut 36 is provided by a hydraulic cylinder 35 in the vicinity of the bush portion through which the tie bar 28 on the outer wall surface of the movable plate 29 is inserted. An actuated half-nut mechanism is provided. A guide rail (not shown) such as a linear motion guide is provided on the bed 12 in the mold opening / closing direction, and the movable platen 29 is guided by the guide rail. The movable platen 29 is guided by the guide rail and the tie bar 28 by a mold opening / closing mechanism and is movable in the mold opening / closing direction. A movable mold 38 is attached to the surface of the movable plate 29 facing the fixed plate 27. An ejector mechanism 40 having a hydraulic cylinder 39 is attached to the back surface of the movable plate 29 (on the opposite side of the attachment surface of the movable mold 38). The actuator of the half nut mechanism or the ejector mechanism 40 may be operated by an electric motor.

Next, the control device 41 and the hydraulic circuit of the injection molding machine 11 will be described with reference to FIG. First, the first pump 42 will be described. The tank 43 is connected to a first pump 42 that can be driven to rotate by controlling the rotation speed of the pump per hour by an inverter 44. The inverter 44 is controlled by the connected control device 41, and the frequency of the inverter 44 is controlled to control the rotation speed of the electric motor 45 (three-phase induction motor). In the present embodiment, the first pump 42 uses a variable displacement axial piston. The angle of the swash plate that changes the discharge capacity of the first pump 42 is switched by a discharge capacity changing cylinder 46 (compensator). Supply of hydraulic oil to the discharge capacity change cylinder 46 is supplied via a discharge capacity switching valve 47. When the supply amount (supply pressure) of hydraulic oil to the discharge capacity change cylinder 46 is small or not, the discharge capacity is set by a spring. The rod of the change cylinder 46 is returned, and the angle of the swash plate becomes zero or minimal.

Further, a first relief valve 50 and a second relief valve 51 which are branched from the pilot pipe 49 of the first pump 42 and have different set pressures are provided in parallel. A switching valve 52 that is electromagnetically operated is provided for the purpose of switching which one of the first relief valve 50 and the second relief valve 51 communicates with the discharge capacity changing cylinder 46. The set pressures of the first relief valve 50 and the second relief valve 51 can be changed via the control device 41 by setting input. The switching valve 52 is also switched by a signal from the control device 41. Thus, the first pump 42 of the present embodiment can be controlled to two set pressures, and the discharge flow rate is a pump that can be closed-loop controlled by an inverter, contributing to energy saving. Further, when the rotational speed of the first pump 42 is lowered, it contributes to noise prevention. The set pressure of the first pump 42 may be one stage or three stages or more.

The first pump 42 is not limited to an axial piston pump, and may be a gear pump or a vane pump. The drive source of the first pump 42 may be a servo motor that performs closed-loop control of the rotation speed, or may be a constant-rotation motor that is constantly rotated by an electric motor that is not subjected to closed-loop control.

A check valve 53 is provided in the pipe line 48 from the first pump 42, and a reducing valve 54 (electromagnetic pressure control valve) that is closed-loop controlled is provided at the tip (the side far from the pump). . Therefore, even if the supply pressure is controlled to one of the two pressures in the first pump 42, the hydraulic oil can be supplied to the mold clamping cylinder 18 and the like by further controlling the pressure to a desired pressure by the reducing valve 54. A pipe 48 branches off from the reducing valve 54. In this embodiment, the clamping cylinder 18 of the clamping mechanism, the hydraulic cylinder 35 of the half nut mechanism, and the hydraulic cylinder 24 for nozzle touch of the nozzle touch mechanism are provided. It is connected. Here, hydraulic oil is supplied to the hydraulic cylinder 39 of the ejector mechanism 40 by a second pump 56 controlled by a servo motor 55 described later, but hydraulic oil may be supplied from the first pump 42.

The hydraulic circuit of each hydraulic cylinder 18, 24, 35, 39 as an actuator will be described. The mold clamping is performed so that hydraulic oil is supplied to the mold clamping oil chamber 18 a of the mold clamping cylinder 18 via the cartridge valve 57. A pipe line on the side oil chamber 18 a side is connected, and a hydraulic pressure sensor 58 is provided on the pipe line on the mold clamping oil chamber 18 a side of the cartridge valve 57. In addition, a pressure relief opening / closing valve 59 is provided in a pipeline branched from the pipeline on the mold clamping oil chamber 18a side. Since the cartridge valve 57 is controlled by the pilot pressure via the pilot pipe 60, an electromagnetically operated switching valve 61 is provided to supply and shut off the pilot pressure of the pilot pipe 60. Similarly, the mold opening oil chamber 18b of the mold clamping cylinder 18 is connected via the cartridge valve 62, and the pipe line on the mold opening oil chamber 18b side of the cartridge valve 62 is connected to the mold opening oil chamber 18b. ing. In addition, a pressure relief opening / closing valve 63 is provided in a pipeline branched from the pipeline on the mold opening oil chamber 18b side. Since the cartridge valve 62 is controlled by the pilot pressure via the pilot pipe 64, the pilot pipe 64 is provided with a switching valve 65 that is electromagnetically operated to supply and shut off the pilot pressure.

The hydraulic cylinder 35 of the half nut mechanism and the hydraulic cylinder 24 for nozzle touch of the nozzle touch mechanism are provided with four-way switching valves 75 and 76 that are electromagnetically operated through the pressure reducing valves 66 and 67 (on the cylinder side). The chamber on the cylinder hydraulic oil supply side can be switched. Although not shown, a hydraulic cylinder may be used for the fixed mold 23 or the movable mold 38 by a gate valve, a core moving mechanism, a mold mounting mechanism, or the like.

Next, the second pump 56 will be described. The tank 43 is connected to the second pump 56 whose servo motor 55 controls the rotation speed of the pump. The second pump 56 is a gear pump having a fixed discharge amount per rotation. The current value of the servo motor 55 of the second pump 56 is controlled by a servo amplifier 68, and the rotational speed of the electric motor per time is closed-loop controlled. Further, the second pump 56 is also excellent in stop and rotation start responsiveness. The servo amplifier 68 is controlled by a signal from the control device 41. The second pump 56 of the present embodiment is a double pump, and one pump 56 a is connected to the hydraulic cylinder 39 of the ejector mechanism 40 with a pipeline 69 and an electromagnetically operated four-way switching valve 70 provided in the pipeline 69. Connected through. The hydraulic cylinder 39 of the ejector mechanism 40 can be controlled with higher accuracy by using a servo valve or other flow control valve with a direction switching function that is controlled by a closed loop instead of the open-control four-way switching valve 70. Is possible. The other pump 56b is connected to a conduit 48 through which hydraulic fluid is sent from the first pump 42 via a conduit 71 and a check valve 72 provided in the conduit 71. The pipes 69 and 71 to which hydraulic oil is supplied from both the pumps 56a and 56b are provided so as to be connectable and disconnectable by the pipe 73 and an on-off valve 74 that is electromagnetically operated. Relief valves 77 and 78 are provided for the pipes 69 and 71 for circuit protection when the servo motor 55 becomes uncontrollable and for unloading one hydraulic oil, respectively. . In this embodiment, the hydraulic cylinder 39 of the ejector mechanism 40 is operated by the second pump 56, but other hydraulic cylinders 35 and the like may be operated by the second pump 56.

The second pump 56 in which the servo motor 55, which is an electric motor, is stopped or rotated at the minimum rotation speed when any actuator other than the mold clamping cylinder 18 is operated is not limited to a gear pump, but is an axial type piston. A pump or a vane pump may be used. The drive source of the second pump 56 may be an electric motor that controls the rotational speed using an inverter. In the present embodiment, a multiple pump is used as the second pump 56, but a single pump may be used. Furthermore, in this embodiment, the pump for supplying the hydraulic oil is composed of two pumps 42 and 56, that is, a first pump 42 and a second pump 56, but further, a third pump, a fourth pump, A plurality of pumps such as a fifth pump may be provided. In the above description, the third pump, the fourth pump, the fifth pump, etc. may be a pump that is always rotated or a pump that stops rotating. Conventionally, a large amount of hydraulic oil is unloaded in the tank while the pump is always operated. However, in the present invention, such a large amount of hydraulic oil is not unloaded, which leads to energy saving.

The injection servo motor 15, the metering servo motor 16, and the servo motor 31 of the mold opening / closing mechanism of the movable platen 29 are also connected to the control device 41 via a servo amplifier (not shown) and closed by the control device 41. Loop control is performed.

Next, a control method of the injection molding machine 11 will be described with reference to FIGS. In the present embodiment, as shown in FIG. 3 as an example, the set pressure of the first relief valve 50 that switches the supply pressure of the first pump 42 is 8 Ma as an example, and the setting of the second relief valve 51 is performed. The pressure is 18 MPa as an example. As shown in FIG. 2, the actuator for moving the movable platen 29 in the mold closing process is performed by a servo motor 31. At this time, the first pump 42 is configured such that the first relief valve 50 and the discharge capacity changing cylinder 46 (compensator) are connected by the switching valve 52. Accordingly, the set pressure of the hydraulic oil sent from the first pump 42 to the pipe 48 is 8 MPa necessary for maintaining the pilot pressure of the pilot pipes 60 and 64, as shown in FIG. The rotational speed of the first pump 42 is also controlled at a low speed by controlling the inverter 44. At this time, when the pressure of the hydraulic fluid in the pipe 48 and the pilot pipe 49 of the first pump 42 approaches 8 MPa, the offset of the first relief valve 50 is activated, and the discharge capacity switching valve 47 is switched from the first relief valve 50. Accordingly, the hydraulic oil supplied to the discharge capacity changing cylinder 46 is increased, the tilt angle of the swash plate of the first pump 42 is switched from the large tilt angle to the small tilt angle, and the cut-off control is performed. Therefore, when the pressure of the hydraulic oil in the pipe line 48 or the like becomes the set pressure or close to the set pressure, the discharge amount per rotation of the first pump 42 is automatically reduced, and the electric motor 45 that drives the first pump 42 Reduces load and leads to energy saving. At this time, the servo motor 55 of the second pump 56 stops rotating. At this time, the servo motor 55 may be rotated at the minimum number of rotations at which the second pump 56 can be slightly rotated.

Next, when the movable platen 29 is closed and a cavity is formed between the fixed mold 23 and the movable mold 38 to complete the mold closing process, the four-way switching valve 66 is actuated to activate the hydraulic cylinder 35 of the half nut mechanism. The half nut 36 is engaged with the engaging portion 34 of the tie bar 28 by operating. Then, the process proceeds to the pressure increasing process. In the pressure increasing process, first, the mold clamping cylinder 18 is operated to move the piston and tie bar 28 to eliminate the gap between the half nut 36 and the locking portion 34. Thereafter, the pressure of the hydraulic oil in the mold clamping side oil chamber 18a is increased to perform mold clamping. At this time, since the clamping cylinder 18 has a large pressure receiving area, it is necessary to supply a large amount of hydraulic oil in order to move the piston and tie bar 28. As an operation of the hydraulic circuit in the pressure increasing process, first, the switching valve 61 is operated and the cartridge valve 57 is operated by the pilot pressure, so that the pipe line 48 side and the mold clamping side oil chamber 18a are communicated.

In the first pump 42, the inverter 44 controls the frequency according to a command from the control device 41 to increase the rotation speed of the electric motor, and rotates the pump at a high speed. Further, the switching valve 52 is switched so that the second relief valve 51 and the discharge capacity changing cylinder 46 (compensator) are connected. As a result, the set pressure of the hydraulic oil supplied from the first pump 42 is changed to 18 MPa. The rotation speed and the set pressure may be changed immediately before or after completion of mold closing, depending on the method of engaging the half nut 36. Further, in the present embodiment, the second pump 56 starts rotating immediately before completion of mold closing, and discharge is performed with the maximum number of rotations simultaneously with completion of mold closing. At this time, the on-off valve 74 is opened and the four-way switching valve 70 to the hydraulic cylinder 39 of the ejector mechanism 40 is closed, so that hydraulic oil is supplied to the mold clamping cylinder 18 from both the dual pumps 56a and 56b. . Note that this supply start may also start rotation of the second pump 56 at the same time as the completion of mold closing or slightly behind.

Therefore, in the present invention, when the mold clamping cylinder 18 that requires the most hydraulic oil is operated (here, pressure increasing operation), the second pump 56 is operated as shown in FIG. The mold clamping cylinder 18 is operated by adding and joining the hydraulic oil from For this reason, even if the clamping cylinder 18 has a large pressure receiving area, it can be operated at a relatively high speed and can be boosted at a relatively high speed.

Then, when the pressure of the hydraulic oil detected by the hydraulic sensor 58 reaches a set pressure (for example, 18 MPa) in the pressure increasing process, the second pump 56 stops rotating. However, since the check valve 72 is provided, even if the second pump 56 is stopped, the hydraulic oil supplied from the first pump 42 does not reach the second rotation speed. There is no back flow to the pump 56 side. At this time, the pressure of the pipe line 48 reaches 18 MPa almost simultaneously or slightly before and after that, the offset of the second relief valve 51 works slightly before that, and the hydraulic oil leaks from the second relief valve 51. The hydraulic oil supplied to the discharge capacity changing cylinder 46 via the discharge capacity switching valve 47 is increased. Then, as shown in FIG. 3, a cutoff control is performed in which the tilt angle of the swash plate of the first pump 42 is switched from a large tilt angle to a small tilt angle. The stop of the second pump 56 is the tilt angle of the first pump 42, a preset timing (sequentially controlled), the mold clamping force detected by the sensor, the position of the mold clamping cylinder 18, etc. It may be stopped by. In the above description, the setting pressure of the mold clamping cylinder 18 is described as an example of 18 MPa which is the same as the setting pressure on the supply side of the first pump 42. However, the setting pressure of the clamping cylinder 18 can be arbitrarily controlled by the reducing valve 54. For example, when the clamping cylinder 18 is controlled at 16 MPa, the setting pressure of the clamping cylinder 18 is set on the supply side of the first pump 42. It is controlled to be different from the set pressure. When the hydraulic sensor 58 detects the set pressure 16 MPa (set pressure of the reducing valve 54) on the mold clamping cylinder 18 side, the operation of the second pump 56 is stopped.

In the next holding step, the mold clamping side oil chamber 18a, the pipe line 48 and the like of the mold clamping cylinder 18 have already been boosted to the set pressure, so that the angle of the swash plate of the first pump 42 is automatically inclined slightly. The state where the turning angle is maintained is continued. The rotational speed of the first pump 42 is maintained at a high speed, although the rotational speed is controlled by the inverter 44. Note that the number of rotations of the first pump 42 may be reduced in the holding step. In the holding step, only the leakage from the clamping cylinder 18 and the hydraulic circuit is replenished so that the pressure of the hydraulic fluid in the clamping-side oil chamber 18a of the clamping cylinder 18 does not decrease. From the above, only a small amount of hydraulic oil is supplied to the mold clamping side oil chamber 18a. When a predetermined delay time elapses, the injection servo motor 15 of the injection device 13 is driven to advance the screw 14, and the molten resin weighed in advance is injected and filled into the cavity. By this time, hydraulic oil is supplied to the nozzle touch hydraulic cylinder 24 to advance the injection device 13 so that the nozzle 20 is brought into contact with the fixed mold 23. Alternatively, depending on the molding method, the nozzle 20 is held in contact with the fixed mold 23. In this case, pressure is sealed in the hydraulic cylinder 24 for nozzle touch. In the present embodiment, the actuator of the injection mechanism of the injection device 13 is driven by the servo motor 15 (electric motor), so that highly accurate control is possible.

In the holding step after injection filling and holding pressure, the molten resin in the cavity is cooled and solidified. In parallel with the cooling and solidification of the molten resin, the injection device 13 keeps the nozzle touched, or retracts the nozzle 20 and closes the nozzle 20 to drive the metering servo motor 16 to move the screw 14. The molten resin is measured for rotation and then injection.

Next, in the depressurization step, the switching valve 61 is switched and the cartridge valve 57 is also closed, so that hydraulic fluid is not supplied from the first pump 42 side to the mold clamping side oil chamber 18a. Then, the on-off valve 59 is opened to return the hydraulic oil in the mold clamping side oil chamber 18a to the tank 43, and the pressure in the mold clamping side oil chamber 18a is set to zero. At the same time or slightly before and after that, the set pressure of the first pump 42 is lowered by switching the switching valve 52. At the same time, the rotation speed of the first pump 42 is changed to low speed rotation by controlling the inverter 44. Note that the rotation speed of the first pump 42 in the depressurization process may remain at a high speed. The second pump 56 remains stopped during the holding process in which the metering is performed in parallel by the injection device 13 and during the depressurizing process.

Next, a powerful mold opening process for opening the movable mold 38 from the fixed mold 23 using the mold clamping cylinder 18 is started. In the powerful mold opening process, the switching valve 65 is switched to operate the cartridge valve 62 to connect the pipe line 48 connected to the pump side and the pipe line connected to the mold opening side oil chamber 18b. At the same time or slightly before and after, the set pressure of the first pump 42 is increased and the inverter 44 is controlled so that the rotational speed of the pump is increased. Also, the hydraulic oil is supplied from the second pump 56 by rotationally driving the servo motor 55 that has been stopped. At this time, the servo motor 55 may be driven to rotate at a low speed from the latter half of the depressurization step.

In the powerful mold opening process, the piston and the rod (tie bar 28) of the mold clamping cylinder 18 are moved in the mold opening direction with a predetermined stroke (for example, about several tens of mm). In this case, speed control is performed. As for speed control, as shown in FIG. 6, the first pump 42 supplies hydraulic fluid to its full capacity, and the rotational speed of the servo motor 55 of the second pump 56 is closed-loop controlled, so that the clamping cylinder 18, the moving speed of the movable plate 29 and the movable mold 38 is controlled. In the powerful mold opening process, the speed control is performed as described above. However, in relation to the pressure, the first pump 42 is controlled to be cut off immediately before the set pressure. The second pump 56 controls the rotation speed and performs speed control. However, when the pressure reaches a set value, the second pump 56 leaks hydraulic oil from the relief valves 77 and 78 (safety valve). The set pressure of the first pump 42 in the powerful mold opening process is controlled by the reducing valve 54, but it may be the same as the set pressure on the first pump 42 side.

In the next mold opening process, the operation of the mold clamping cylinder 18 is stopped, the engagement between the half nut 36 and the engaging portion 34 of the tie bar 28 is released, and then the servo motor 31 of the mold opening / closing mechanism is driven to move the movable plate 29 and The movable mold 38 is moved to the mold opening completion position. At this time, the first pump 42 is set to a low speed and a low rotation speed, and the second pump 56 is stopped.

When the movable platen 29 and the movable mold 38 are stopped at the mold opening completion position and the mold opening process is completed, the ejecting mechanism 40 then projects the molded product and transfers it with an unillustrated unloading device. In the extraction step, the servo motor 55 of the second pump 56 is driven to rotate in order to operate the ejector mechanism 40. At this time, the relief valve 78 is opened, the hydraulic oil of the pump 56b is unloaded to the tank, and only the hydraulic oil of the pump 56a is supplied to the hydraulic cylinder 39 of the ejector mechanism 40 via the four-way switching valve 70. At this time, since the on-off valve 74 is closed and the check valve 72 is provided, there is no inflow of hydraulic oil from the first pump side 42. Accordingly, as shown in FIG. 7, the ejector mechanism 40 is speed controlled by controlling the rotation speed of the servo motor 55 of the second pump 56. At this time, the ejector mechanism 40 can be controlled with higher accuracy by using a servo valve or other flow control valve with a direction switching function that is controlled by a closed loop instead of the four-way switching valve 70. Note that when the ejector mechanism 40 is operated by an electric motor, the second pump 56 is not operated. Further, the ejector mechanism 40 may be operated by hydraulic oil supplied from the first pump 42.

As described above, in the present invention, in the first pump 42, the electric motor 45 is always rotated in order to operate the hydraulic cylinders 17, 24, 35 and hold pilot pressures such as the pilot pipes 60, 64. Further, the second pump 56 is provided with any actuator other than the mold clamping cylinder 18 (for example, the servomotor 15 for injection, the servomotor 16 for metering, the servomotor 31 for mold opening / closing, and the hydraulic pressure for the half nut. If the electric motor (servo motor 55) is stopped or rotated at the minimum number of rotations when the cylinder 35 or the like is operated, and the supply of hydraulic oil is insufficient only from the first pump 42, at least higher than the minimum number of rotations. It is driven to rotate and supplies hydraulic oil.

Therefore, for example, when the mold opening / closing mechanism is operated by a hydraulic cylinder in addition to the mold clamping cylinder 18 of the mold clamping device 17, the hydraulic cylinder for mold opening / closing needs to supply a large amount of hydraulic oil. In the closing process and the mold opening process, the second pump 56 is rotationally driven to supply hydraulic oil. In the present invention, when the injection device 13 is operated by an electric motor, a hydraulic cylinder that supplies a large amount of hydraulic oil on the mold clamping device 17 side is used together with the second motor 56 using the servo motor 55 to supply the hydraulic oil. The hydraulic oil is supplied to the hydraulic cylinder (except for the hydraulic cylinder 39 of the ejector mechanism 40 in the present embodiment) and the pilot pipe with a small supply amount of hydraulic oil. Energy saving can be realized by supplying hydraulic oil by the first pump 42.

The present invention is not enumerated one by one, but is not limited to that of the above-described embodiment, and it goes without saying that those skilled in the art also apply modifications made in accordance with the spirit of the present invention. is there. The size and structure of the injection molding machine targeted by the present invention are not limited. However, as an example, the injection molding machine is a large-sized injection molding machine having a clamping force of 800 t or more, and is clamped by a clamping cylinder without using a toggle mechanism. It is suitably used for those that perform tightening. The injection molding machine may be a vertical injection molding machine in which the movable plate moves up and down in the vertical direction. The injection molding machine may have a rotary table attached to a movable platen. Furthermore, the number of injection devices is not limited to one, and a multicolor molded product may be formed using a plurality of injection devices. Furthermore, in the case of injection molding machines that mold multicolor molded products, in addition to the fixed platen and movable platen, a fixed intermediate plate is installed between the fixed platen and the movable platen. The mold and the intermediate mold attached to the intermediate plate, and the intermediate mold attached to the intermediate plate and the movable die attached to the movable plate are molded with different resins, respectively, and then the intermediate plate and the intermediate plate A multicolor molded product may be molded by rotating the mold and molding in the same manner.

The injection molding machine may perform injection compression molding or foam molding in the above. In the case of performing injection compression molding, an accumulator may be provided in the hydraulic circuit to increase the pressure at a high speed during mold clamping. In the injection compression molding or foam molding, pressure control for detecting the value of the pressure sensor to control the rotation speed of the servo motor or pressure control for controlling the reducing valve may be performed. In the case of using four mold clamping cylinders, parallel control may be performed by individually controlling each mold clamping cylinder with a valve capable of closed loop control such as a servo valve during compression molding. The injection molding machine may be used for various molded products such as metal molded products, inorganic molded products, and organic molded products other than resin, in addition to resin molded products.

DESCRIPTION OF SYMBOLS 11 Injection molding machine 13 Injection apparatus 14 Screw 15, 16, 31, 55 Servo motor 17 Mold clamping apparatus 18 Mold clamping cylinder 42 1st pump 44 Inverter 45 Electric motor 54 Reducing valve 56 2nd pump

Claims (4)

In an injection molding machine in which the operation of the screw of the injection device is performed by an electric motor and the operation of the clamping cylinder of the clamping device is hydraulically operated,
Servo motor for injection,
Servo motor for weighing,
A first pump in which the electric motor of the drive source is always rotated;
A second pump in which the electric motor of the drive source is stopped or rotated at the minimum number of rotations when any actuator other than the mold clamping cylinder is operated,
An injection molding machine characterized in that hydraulic cylinders from a first pump and hydraulic oil from a second pump are joined to operate a clamping cylinder . The mold opening / closing mechanism of the mold clamping device is operated by a servo motor of the mold opening / closing mechanism, and the rotation of the second pump is stopped or rotated at the minimum number of rotations for at least a majority of the operation time of the mold opening / closing mechanism. The injection molding machine according to claim 1. 3. The injection molding according to claim 1, wherein the first pump has an inverter that controls the rotational speed of the pump, and the second pump has a servo motor that controls the rotational speed of the pump. Machine. The injection according to any one of claims 1 to 3, wherein the clamping cylinder is operated by a valve operated by a pilot pressure, and the pilot pressure is secured by the operation of the first pump. Molding machine.